1. Field of the Invention
The present invention relates generally to an apparatus for transferring a number of semiconductor wafers. More particularly, the present invention relates to an apparatus for transferring a number of semiconductor wafers to a furnace tube in one of a plurality of vertical type dispersing furnaces via a wafer boat charging/discharging unit.
2. Description of the Related Art
In general, a variety of semiconductor elements are produced by way of a large number of processing steps. One of the processing steps is a step of allowing a number of semiconductor wafers to be subjected to dispersing.
FIG. 8 is a perspective view which illustrates a conventional vertical type dispersing furnace including a furnace tube in which a dispersing step is to be performed. In the drawing, the vertical type dispersing furnace is represented by reference numeral 1. A furnace tube 2 is accommodated in the upper part of the dispersing furnace 1, and a vertically displaceable wafer boat stage 3 is disposed below the furnace tube 2 to elevate and lower a mass of semiconductor wafers. A wafer boat 4 is placed on the wafer boat stage 3 in an upright standing state, and a number of semiconductor wafers 5 are received in the wafer boat 4 in a laminated structure in a parallel relationship relative to each other. Thus, the respective semiconductor wafers 5 are held in a horizontal attitude when the wafer boat 4 stands upright as shown in the drawing.
In operation, after a predetermined number of semiconductor wafers 5 are received in the wafer boat 4 by manually handling a pincette or the like tool, the wafer boat stage 3 is elevated so as to allow the wafer boat 4 to be charged in the furnace tube 2. While the foregoing state is maintained, the respective semiconductor wafers 5 are subjected to dispersing in the furnace tube 2. Thereafter, the wafer boat stage 3 is lowered so that the semiconductor wafers 5 which have been subjected to dispersing are taken out from the wafer boat 4 by manually handling the pincette or the like tool.
With the conventional vertical type dispersing furnace 1 as constructed in the above-described manner, however, it has been found that there arise such problems that the semiconductor wafers 5 are undesirably injured or damaged when they are manually handled by the pincette or the like tool, and moreover, fine dust or other foreign material becomes adhesively attached to the semiconductor 5.
In addition, since the semiconductors 5 are manually charged in and discharged from the wafer boat 4, and since the wafer boat 4 is likewise manually mounted on and dismounted from the wafer boat stage 3, an operator is required to conduct his work using much care, such that the operational efficiency is remarkably being reduced. These problems become more and more serious as the respective semiconductor wafers 5 are dimensioned to have a larger diameter.